Modern vehicles include a vast array of sensors, such as air bag sensors, tire pressure sensors, engine sensors, seat belt sensors, and many others. The air bag sensors, for example, provide data about the vehicle's operation (e.g., wheel speed, deceleration, etc.) to an automotive control unit (ACU). Based on the data received from the air bag sensors, the ACU can determine when air bags within a vehicle should be deployed.
FIG. 1 shows a vehicular sensing system 100 including a sensor interface module 102. The sensor interface module 102 has a control unit interface 104 coupled to an automotive control unit 106 and a sensor interface 108 coupled to a pair of wires 110, 112 that are connected to one or more sensors 114 (e.g., 114a, . . . 114n). To limit noise and attenuate the line resonance, an RLC network 116 can be coupled to the sensor interface 108.
To transmit information to the sensors 114, the sensor interface module 102 includes a modulation unit 118, which modulates a supply voltage (e.g., a change in the DC supply voltage) to transmit information to at least one of the sensors 114. When data is not transmitted, the modulation unit 118 often provides an un-modulated (e.g., DC) supply voltage to the sensors 114. To receive information from the sensors 114, the sensor interface module 102 includes a demodulation unit 120, which demodulates a modulated sensor current signal to receive information from at least one of the sensors 114.
A physical interface layer 122 may be positioned between the modulation and demodulation units, 118 and 120, and wires 110 and 112 in order to allow for a current measurement to be made by the demodulation unit 120, which is connected in parallel to the modulation unit 118. The physical interface layer 122 may also include filters for antialiasing of input signals or for removing quantization noise from an output signal. It can also include measures to assure EMC and ESD compliance and protection against short circuits, or switches to change between different supplies. These functions are only examples and should not be seen as restrictions.